Sheet stacking apparatus, method for controlling sheet stacking apparatus, and storage medium

ABSTRACT

A sheet stacking apparatus includes a lowering control unit, determination unit, setting unit, and notification unit. The lowering control unit can lower a sheet stacking unit according to a sheets stacked amount. The determination unit can determine that the sheet stacking unit cannot be lowered. The setting unit sets whether to prompt a user to remove an object placed under the sheet stacking unit if the determination unit determines that the sheet stacking unit cannot be lowered while sheets are being stacked thereon. If it is set to prompt the user to remove the object placed under the sheet stacking unit, the notification unit makes a notification for prompting the user to remove the object placed under the sheet stacking unit, and if it is not set to prompt the user to remove the object placed under the sheet stacking unit, the notification unit does not make the notification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet stacking apparatus that can stack sheets on a sheet stacking unit, a method for controlling the sheet stacking apparatus, and a storage medium.

2. Description of the Related Art

There is a conventional sheet stacking apparatus that discharges sheets to an elevatable sheet stacking unit.

Such a sheet stacking apparatus prints an image on a sheet and discharges the image-printed sheet from a sheet discharge port to the sheet stacking unit. Each time a sheet is discharged to the sheet stacking unit, the sheet stacking unit is lowered so that the topmost surface of sheets stacked on a tray is positioned near the sheet discharge port. This enables stable stacking of sheets discharged from the sheet discharge port.

If an obstacle obstructing the lowering of the sheet stacking unit is placed under the sheet stacking unit, the sheet stacking unit collides with the obstacle when the sheet stacking unit is lowered. Even after the collision with the obstacle, if an attempt to lower the sheet stacking unit is made, a load is imposed on a driving unit for lowering the sheet stacking unit, whereby the sheet stacking unit and/or the driving unit can be broken.

A technique for stopping a sheet discharge operation and the lowering operation of the sheet stacking unit and displaying a warning to remove an obstacle if the lowering operation of the sheet stacking unit is obstructed by the obstacle, has been known (Japanese Patent Application Laid-Open No. 2001-226022).

According to the conventional technique, when the warning is displayed, the user removes the obstacle and the sheet stacking operation is performed without the obstacle.

A place under the sheet stacking unit is close to the sheet stacking apparatus and easily accessible to the user. It is possible that the administrator of the sheet stacking apparatus may therefore want to use the sheet stacking apparatus such as intentionally placing replenishment sheet stacks, instruction manuals, and/or boxes of toner bottles under the sheet stacking unit.

In such a case, when the lowering operation of the sheet stacking unit is obstructed, the administrator may demand the removal of an obstacle. The user unaware of his intention may then arbitrarily move the replenishment sheet stacks, the instruction manuals, and/or the boxes of toner bottles placed under the sheet stacking unit.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a sheet stacking apparatus includes a lowering control unit configured to lower a sheet stacking unit according to an amount of sheets stacked, a determination unit configured to determine that the sheet stacking unit cannot be lowered by the lowering control unit, a setting unit configured to set whether to prompt a user to remove an object placed under the sheet stacking unit if the determination unit determines that the sheet stacking unit cannot be lowered while sheets are being stacked on the sheet stacking unit, and a notification unit configured to, if it is set by the setting unit to prompt the user to remove the object placed under the sheet stacking unit, make a notification for prompting the user to remove the object placed under the sheet stacking unit, and if it is not set by the setting unit to prompt the user to remove the object placed under the sheet stacking unit, not make the notification.

A sheet stacking apparatus sets whether to prompt removal of an object placed under a sheet stacking unit if lowering of the sheet stacking unit is obstructed by the object. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a printing system according to a first exemplary embodiment.

FIG. 2 is a sectional view illustrating a configuration of a multifunction peripheral (MFP) according to the present exemplary embodiment.

FIG. 3 is a diagram for describing an operation unit according to the present exemplary embodiment.

FIG. 4 is a flowchart for describing a control example according to the present exemplary embodiment.

FIG. 5 is a flowchart for describing a control example according to the present exemplary embodiment.

FIG. 6 is a flowchart for describing a control example according to the present exemplary embodiment.

FIG. 7 is a flowchart for describing a control example according to the present exemplary embodiment.

FIG. 8 is a diagram for describing a screen according to the present exemplary embodiment.

FIG. 9 is a diagram for describing a screen according to the present exemplary embodiment.

FIG. 10 is a diagram for describing a screen according to the present exemplary embodiment.

FIG. 11 is a diagram for describing a screen according to the present exemplary embodiment.

FIG. 12 is a sectional view illustrating the configuration of the MFP according to the present exemplary embodiment.

FIG. 13 is a flowchart for explaining a control example according to a second exemplary embodiment.

FIG. 14 is a diagram for describing a screen according to the first exemplary embodiment.

FIG. 15 is a diagram for describing a screen according to a third exemplary embodiment.

FIG. 16 is a flowchart for describing a control example according to the present exemplary embodiment.

FIG. 17 is a flowchart for describing a control example according to the present exemplary embodiment.

FIG. 18 is a flowchart for describing a control example according to a fourth exemplary embodiment.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram illustrating a printing system according to a first exemplary embodiment. The printing system according to the present exemplary embodiment includes a personal computer (PC) 111 and an MFP 100 which is an example of a sheet stacking apparatus.

The MFP 100 according to the present exemplary embodiment includes a control unit 110, a reader unit 200, and a printer unit 300. While the present exemplary embodiment is described by using an MFP as an example, a single functional peripheral (SFP) may also be used as long as the SFP includes a printing function of the printer unit 300. The reader unit 200, the control unit 110, and the printer unit 300 are electrically connected to transmit and receive control commands and data to/from each other. A sheet discharge unit 330 is configured to be detachably attachable to the MFP 100.

The control unit 110 includes a central processing unit (CPU) 120, an image memory 130, a nonvolatile memory 140, a random access memory (RAM) 150, a read-only memory (ROM) 160, an operation unit 170, and a timer 180.

The CPU 120 controls the MFP 100 in a comprehensive manner by reading a program stored in the ROM 160 into the RAM 150 and executing the program.

The RAM 150 functions as a work area of the CPU 120. The RAM 150 stores various programs and data.

The ROM 160 stores various programs to be read and executed by the CPU 120.

The image memory 130 is a memory intended to store image data. For example, the image memory 130 stores image data read by the reader unit 200 and image data received from the PC 111. The image data stored in the image memory 130 is transmitted to the printer unit 300 according to instructions from the CPU 120.

The nonvolatile memory 140 functions as a storage unit that retains data even without power supply. The nonvolatile memory 140 stores various programs and image data. The nonvolatile memory 140 may be a hard disk drive (HDD), a digital versatile disk (DVD), a solid state drive (SSD), a Blu-ray Disc, or the like having sufficient capacity to store image data.

The operation unit 170 includes a display unit and hard keys. The operation unit 170 displays an operation screen and accepts operations from the user.

The timer 180 is used to measure time.

A network interface (I/F) 190 performs control for the MFP 100 to communicate with an external apparatus such as the PC 111 via a network 112. The following description will be given by using the PC 111 as an example of the external apparatus, whereas the external apparatus may also be another MFP, a mobile terminal, or a facsimile apparatus. The present exemplary embodiment deals with a case where the MFP 100 and the external apparatus are connected via the wired network 112. However, the MFP 100 and the external apparatus may be connected via a Universal Serial Bus (USB) cable. The MFP 100 and the external apparatus may be configured to be able to communicate by wireless communications such as WiFi.

The reader unit 200 includes a scanner unit 210 and a document feeding unit (DF unit) 250. The scanner unit 210 reads an image of a document and generates image data expressing the read image. The document feeding unit 250 is intended to convey a document for the scanner unit 210 to read.

The printer unit 300 is a unit for printing an image on a sheet (recording paper). The printer unit 300 feeds sheets stored in a sheet feeding unit 310 one by one, and conveys the sheet to a marking unit 320. The sheet feeding unit 310 includes cassettes 311 to 314 and a manual feed tray 315.

The marking unit 320 prints an image on the fed sheet based on the image data transmitted from the image memory 130. The marking unit 320 may be an electrophotographic marking unit or an inkjet marking unit. Other methods capable of printing an image may also be used.

The printer unit 300 conveys the image-printed sheet to the sheet discharge unit 330. The sheet discharge unit 330 includes a stacking tray 507, and discharges the conveyed sheet to the stacking tray 507. The stacking tray 507 is an example of a sheet stacking unit. The stacking tray 507 may be referred to as a sheet discharge tray. A CPU 591 controls the sheet discharge unit 330 according to instructions from the CPU 120. An elevating motor 561 is a motor for lifting and lowering the stacking tray 507. A motor drive control unit 562 is a control unit for driving the elevating motor 561. Forward rotations of the elevating motor 561 lift the stacking tray 507. Reverse rotations of the elevating motor 561 lower the stacking tray 507. The motor drive control unit 562 operates according to instructions from the CPU 120. Tray detection sensors 571 are sensors for detecting a position (height) of the stacking tray 507. A sheet detection sensor 581 is a sensor for detecting the presence or absence of sheets stacked on the stacking tray 507. A height detection sensor 582 is a sensor for detecting the height of the sheets stacked on the stacking tray 507.

In FIG. 1, the sheet discharge unit 330 is illustrated which includes the CPU 591. However, the CPU 591 is not necessarily needed. The CPU 120 may directly control the sheet display unit 330.

Next, details of the MFP 100 described in FIG. 1 will be described with reference to FIG. 2.

The document feeding unit 250 of the reader unit 200 feeds documents set on a document tray one by one and conveys the document to an optical unit 213. The document conveyed to the optical unit 213 is discharged to a sheet discharge tray 219.

When a document is conveyed above the optical unit 213, the reader unit 200 turns on a lamp 212 so that the optical unit 213 irradiates the document with light. Reflected light from the document is guided to a charge-coupled device (CCD) image sensor (hereinafter, referred to as CCD) 218 by mirrors 214, 215, and 216, and a lens 217. The CCD 218 reads an image of the document. Image data output from the CCD 218 is subjected to predetermined processing before transferred to the control unit 110.

The reader unit 200 reads an image of a document placed between the document feeding unit 250 and a platen glass 211. In such a case, the reader unit 200 turns on the lamp 212 and moves the optical unit 213. Reflected light from the document is guided to the CCD 218 by the mirrors 214, 215, and 216, and the lens 217. The CCD 218 reads an image of the document. Image data output from the CCD 218 is subjected to predetermined processing before transferred to the control unit 110. While the present exemplary embodiment deals with a case where the image of the document is read by the CCD 218, a contact image sensor (CIS) may also be used to read the image of the document. If the CIS is used to read the image of the document, the mirrors 214, 215, and 216, and the lens 217 are not needed. The CIS is arranged in the position of the optical unit 213.

The printer unit 300 includes a laser driver 321 which drives a laser light emission unit 322. The laser driver 321 makes the laser light emission unit 322 emit laser light according to the image data output from the image memory 130 of the control unit 110. A photosensitive drum 323 is irradiated with the laser light, whereby a latent image according to the laser light is formed on the photosensitive drum 323. A developing unit 324 makes a developer adhere to the latent image portions of the photosensitive drum 323.

The printer unit 330 includes the drawer-shaped cassettes 311 to 314 and the manual feed tray 315 as the sheet feeding unit 310. The printer unit 300 feeds a sheet from any one of the cassettes 311 to 314 and the manual feed tray 315, and conveys the sheet to a transfer unit 325 through a conveyance path 331. The transfer unit 325 transfers the developer adhering to the photosensitive drum 323 to the sheet.

A conveyance belt 326 conveys the developer-transferred sheet to a fixing unit 327. The fixing unit 327 fixes the developer on the sheet by heat and pressure. The sheet passed through the fixing unit 327 is then discharged through conveyance paths 335 and 334. In a case of discharging the sheet with the print side down, the sheet is guided to a conveyance path 338 through a conveyance path 336. The sheet then can be conveyed in an opposite direction through a conveyance path 337 and the conveyance path 334.

If two-sided printing is set, the sheet passed through the fixing unit 327 is passed through the conveyance path 336 and guided to a conveyance path 333 by a flapper 329. The sheet is then conveyed in an opposite direction and guided to the conveyance path 338 by the flapper 329 before guided to a re-feed conveyance path 332. The sheet guided to the re-feed conveyance path 332 is passed through the conveyance path 331 at the foregoing timing and conveyed to the transfer unit 325. Here, the transfer unit 325 transfers the developer to a second surface different from a first surface. The first surface refers to the surface to which an image has been transferred before by the transfer unit 325. The sheet is guided to the conveyance path 334 through the fixing unit 327.

The sheet conveyed through the conveyance path 334 is conveyed to the sheet discharge unit 330 regardless of whether one-sided printing or two-sided printing is carried out.

The sheet conveyed to the sheet discharge unit 330 is initially delivered to a buffer unit 501. Here, the conveyed sheet is wrapped around a buffer roller and buffered according to circumstances. For example, if time-consuming stapling processing is to be carried out on a downstream side, the buffer unit 501 can be used to adjust the conveyance interval of sheets conveyed from the main unit of the MFP 100.

The sheet is then passed through a conveyance path 504 and stacked on a stack tray 505 by an upstream discharge roller pair 502 and a downstream discharge roller pair 503. If a bundle of sheets for a single copy is stacked on the stack tray 505, the stacked bundle of sheets is discharged to the stacking tray 507.

If an instruction for a shift is issued, the bundle of sheets stacked on the stack tray 505 is discharged to the stacking tray 507 so that the bundle is shifted by 1 cm from the bundle of sheets discharged immediately before. This makes the boundary between the copies clear to the user. The shift width between the bundles of sheets may be other than 1 cm.

If stapling is instructed, a stapling unit 506 performs stapling processing on a bundle of sheets which have been conveyed by the upper discharge roller pair 502, passed through the conveyance path 504 by the downstream discharge roller pair 503, and stacked on the stack tray 505. The stapled bundle of sheets is discharged to the stacking tray 507 by the downstream discharge roller pair 503.

The stacking tray 507 is fixed to a belt 554. The belt 554 is stretched between an upper pulley 551 and a lower pulley 552. The belt 554 has recesses and protrusions, and is stretched so that the recesses and protrusions mesh with those of the upper pulley 551 and the lower pulley 552. As the upper pulley 551 moves, the belt 554 moves accordingly. The elevating motor 561 of FIG. 1 is driven to rotate the upper pulley 551 clockwise or counterclockwise in FIG. 2. Specifically, forward rotations of the elevating motor 561 rotate the upper pulley 551 clockwise in FIG. 2, and the belt 554 moving with the upper pulley 551 lifts the stacking tray 507. Reverse rotations of the elevating motor 561 rotate the upper pulley 551 counterclockwise in FIG. 2, and the belt 554 moving with the upper pulley 551 lowers the stacking tray 507. The lower pulley 552 moves according to the movement of the belt 554, without transmitting the power from the elevating motor 561. The lower pulley 552 may also be configured to be moved by the power transmitted from the elevating motor 561.

The height detection sensor 582 is a sensor for measuring the distance to the top surface of the stacking tray 507 or the distance to the top surface of the stacked sheets. Specifically, if there is no sheet stacked on the stacking tray 507, the height detection sensor 582 measures the distance to the top surface of the stacking tray 507 by irradiating the top surface of the stacking tray 507 with infrared rays and measuring the amount of infrared rays about which the reflection is detected. If there are sheets stacked on the stacking tray 507, the height detection sensor 582 measures the distance to the top surface of the sheets by irradiating the sheets stacked on the stacking tray 507 with infrared rays and measuring the amount of infrared rays about which the reflection is detected. The CPU 120 then performs control to lower the stacking tray 507 or to lift the stacking tray 507 by the elevating motor 561 so that the distance to the top surface of the stacking tray 507 or the top surface of the sheets becomes constant. In other words, the stacking tray 507 descends or ascends according to the amount of sheets stacked on the stacking tray 507. If sheets are discharged, the stacking tray 507 descends. If the sheets on the stacking tray 507 are removed, the stacking tray 507 ascends.

The sheet detection sensor 581 is a sensor for detecting the presence or absence of sheets stacked on the stacking tray 507. The sheet detection sensor 581 detects the presence of the sheets on the stacking tray 507 by detecting that a switch protruding above from the stacking tray 507 is pressed down by the weight of the sheets. The switch can be sufficiently pressed down by the weight of a single sheet. If there is a sheet or sheets on the stacking tray 507, the sheet detection sensor 581 transmits a signal indicating the presence of the sheet(s) to the CPU 120. If there is no sheet, the sheet detection signal 581 transmits a signal indicating the absence of a sheet to the CPU 120. The CPU 120 receives the signal from the sheet detection sensor 581 and determines whether there is a sheet or sheets on the stacking tray 507.

A plurality of tray detection sensors 571 is provided to detect the position of the stacking tray 507. The CPU 120 recognizes the position of the stacking tray 507 according to the tray detection sensor 571 detecting the stacking tray 507.

The tray detection sensors 571 include a top end sensor 573 at the top. The top end sensor 573 is located at an upper limit height to which the stacking tray 507 can be lifted, and detects that the stacking tray 507 is in the highest position (maximum lifting position). The tray detection sensors 571 include a bottom end sensor 574 at the bottom. The bottom end sensor 574 is located at a lower limit height (maximum lowering position) to which the stacking tray 507 can be lowered, and detects that the stacking tray 507 is in the lowest position.

Next, the operation unit 107 of the MFP 100 illustrated in FIG. 1 will be described with reference to FIG. 3.

The operation unit 170 includes a key input unit 601 and a touch panel unit 602. The key input unit 601 accepts user operations using hard keys. The touch panel unit 602 can display soft keys (display keys) and accepts user operations using the soft keys.

The key input unit 601 will initially be described. The key input unit 601 includes an operation unit power switch 603. If the MFP 100 is in a standby mode (normal power state) and the user presses the operation unit power switch 603, the CPU 120 switches the MFP 100 from the standby mode to a sleep mode (a state where power consumption is lower than in the normal power state). If the MFP 100 is in the sleep mode and the user presses the operation unit power switch 603, the CPU 120 switches the MFP 100 from the sleep mode to the standby mode.

A start key 605 is a key for accepting instructions from the user to make the MFP 100 execute copy or data transmission.

A stop key 605 is a key for accepting instructions from the user to make the MFP 100 discontinue copy or data transmission.

A numerical keypad 606 includes keys with which the user registers numerals for various settings.

Next, the touch panel unit 602 will be described. The touch panel unit 602 includes a liquid crystal display (LCD) and a touch panel sheet. The touch panel sheet is attached onto the LCD and includes transparent electrodes. The touch panel unit 602 has a function of displaying an operation screen to accept various settings from the user, and a function of notifying the user of the state and error messages of the MFP 100. The present exemplary embodiment deals with a case where the operation unit 170 includes both the touch panel unit 602 and the key input unit 601. However, an exemplary embodiment of the present invention is not limited thereto. For example, the operation unit 170 may include only the touch panel unit 602 without installing the key input unit 601. The touch panel unit 602 may display keys having the same functions as the keys in the key input unit 601 when needed.

The MFP 100 having the foregoing configuration can execute a plurality of types of jobs.

For example, the MFP 100 executes a copy job. A copy job includes reading an image of a document by using the reader unit 200, generating image data expressing the read image of the document, and printing an image on a sheet based on the image data and settings accepted via the operation unit 170.

The MFP 100 executes a print job. A print job includes analyzing print data received from the PC 111, generating image data based on print settings accepted from the PC 111, and printing an image on a sheet based on the generated image data.

The MFP 100 executes a fax print job. A fax print job includes receiving code data from an external facsimile apparatus via a telephone line, converting the received code data into image data, and printing an image on a sheet based on the converted image data.

The MFP 100 accepts and stores a plurality of such jobs in the nonvolatile memory 140 in sequence, and executes the jobs in the order of storage in the nonvolatile memory 140.

While the MFP 100 has been described to execute a plurality of types of jobs, an exemplary embodiment of the present invention is not limited thereto. The MFP 100 may be able to execute only some types of jobs.

Each time a sheet is discharged to the stacking tray 507, the CPU 120 of the MFP 100 detects the top surface of sheets by using the height detection sensor 582 and drives the elevating motor 561 to lower the stacking tray 507. This can prevent the sheets discharged to the stacking tray 507 from clogging up the sheet discharge port to interfere with the discharging of a sheet. Lifting and lowering the stacking tray 507 to position the topmost surface of the sheets near the discharge port has the advantage that the sheets discharged from the discharge port can be stably stacked. The present exemplary embodiment deals with a case where the stacking tray 507 is lowered each time a sheet is discharged. However, the stacking tray 507 may be lowered each time a bundle of two or more, a predetermined number of sheets is discharged. For example, the stacking tray 507 may be lowered each time ten sheets are discharged.

Suppose that an obstacle (an object) obstructing the lowering of the stacking tray 507 is placed under the elevatable stacking tray 507 as illustrated in FIG. 12. In such a case, the stacking tray 507 collides with the obstacle and cannot be lowered any more. A further attempt to lower the stacking tray 507 applies a load to the stacking tray 507 and the elevating motor 561, whereby the stacking tray 507 and/or the elevating motor 561 can be broken.

If the tray detection sensors 571 detect that the position of the stacking tray 507 does not vary despite driving of the elevating motor 561, the CPU 120 determines that there is an obstacle under the stacking tray 507, and stops printing and lowering the stacking tray 507.

As a result, the stacking tray 507 and the elevating motor 561 can be prevented from being broken even if the stacking tray 507 is forced to lower despite the presence of the obstacle.

After the occurrence of an obstacle detection error, the sheets stacked on the stacking tray 507 may be removed. In the present exemplary embodiment, if the CPU 120 detects the removal of the sheets, the CPU 120 starts to lift the stacking tray 507. The CPU 120 then resumes printing, discharges sheets on the stacking tray 507 and gradually lowers the stacking tray 507. This can hold down a decrease in productivity.

As print products are stacked on the stacking tray 507 again, the stacking tray 507 descends gradually to collide with the obstacle again. A load is applied to the stacking tray 507 and the elevating motor 561, increasing the possibility of breakdown of the stacking tray 507 and the elevating motor 561. The greater the number of collisions with the obstacle, the more load is imposed on the stacking tray 507 and the elevating motor 561, and the higher the possibility of breakdown of the stacking tray 507 and the elevating motor 561 becomes.

In the present exemplary embodiment, when the stacking tray 507 is detected to collide with an obstacle and cannot be lowered, the position of the stacking tray 507 at that time is stored. When lowering the stacking tray 507 again, the lowering operation of the stacking tray 507 is stopped at the stored position. This can hold down a decrease in productivity and prevent the stacking tray 507 from being easily broken.

The place under the stacking tray 507 is close to the MFP 100 and easily accessible to the user. The administrator (or user; hereinafter, the administrator may be referred to as a user) of the MFP 100 may therefore want to place sheet stacks under the stacking tray 100 so that the MFP 100, when running short of sheets, can be immediately replenished with the sheet stacks. The administrator may want to place instruction manuals under the stacking tray 507 in case the user is not sure how to operate the MFP 100.

If a warning about the obstruction of the lowering operation of the stacking tray 507 is displayed even in such cases, the replenishment sheet stacks or the instruction manuals placed under the stacking tray 507 can be arbitrarily moved despite the intension of the administrator.

According to the MFP 100 of the present exemplary embodiment, the administrator sets in advance whether to prompt the removal of an obstacle if the obstacle is detected when the stacking tray 507 is lowered, via a screen illustrated in FIG. 14 before the sheet stacking operation.

FIG. 14 illustrates a screen displayed on the touch panel unit 602 of the operation unit 170 when a user mode key of the operation unit 107 illustrated in FIG. 3 is pressed.

Suppose that the user selects a “prompt removal of obstacle” key 1401 and presses an OK key 1403 on the screen illustrated in FIG. 14. In such a case, the CPU 120 stores information indicating that a setting is made for prompting the removal of an obstacle when the obstacle is detected, into the nonvolatile memory 140.

Suppose that the user selects a “do not prompt removal of obstacle” key 1402 and presses the OK key 1403. In such a case, the CPU 120 stores information indicating that a setting is made for not prompting the removal of an obstacle when the obstacle is detected, into the nonvolatile memory 140.

If the user presses a cancel key 1404, the CPU 120 ends displaying the screen of FIG. 14 without storing either the information indicating the setting for prompting the removal of an obstacle or the information indicating the setting for not prompting the removal of an obstacle into the nonvolatile memory 140.

Subsequently, if an obstacle is detected when the stacking tray 507 is lowered in a sheet stacking operation and the information indicating the setting for prompting the removal of an obstacle is stored in the nonvolatile memory 140, the CPU 120 prompts the removal of the obstacle.

On the other hand, if an obstacle is detected when the stacking tray 507 is lowered for a sheet stacking operation and the information indicating the setting for prompting the removal of an obstacle is not stored in the nonvolatile memory 140, the CPU 120 does not prompt the removal of the obstacle.

By such control, if the administrator wants the user to use the MFP 100 by removing an obstacle when the obstacle is detected during a sheet stacking operation, the administrator can make the setting for prompting the removal of an obstacle. If the administrator wants the MFP 100 to be used with an obstacle intentionally placed under the stacking tray 507, the administrator can make the setting for not prompting the removal of an obstacle.

Next, the control of the CPU 120 according to the present exemplary embodiment will be described with reference to the flowcharts illustrated in FIGS. 4 to 7. The processing illustrated in the flowcharts of FIGS. 4 to 7 is performed by the CPU 120 reading a program stored in the ROM 160 into the RAM 150 and executing the program.

In step S1010, the CPU 120 determines whether a job to be printed is stored in the nonvolatile memory 140. If it is determined that such a job is stored (YES in step S1010), the CPU 120 advances the processing to step S1020. If it is determined that no such job is stored (NO in step S1010), the CPU 120 repeats the processing of step S1010. Examples of the job to be printed include the foregoing copy job, print job, and fax print job.

In step S1020, the CPU 120 feeds a sheet from any one of the cassettes 311 to 314 and the manual feed tray 315. The CPU 120 then controls the marking unit 320 to print an image on the fed sheet based on image data on the job and print settings.

In step S1030, the CPU 120 makes the sheet discharge unit 330 discharge the sheet to the stacking tray 507.

In step S1040, the CPU 120 detects the top surface of sheets stacked on the stacking tray 507 by using the height detection sensor 582. The CPU 120 then issues an instruction to the motor drive control unit 562 of the sheet discharge unit 330 to drive the elevating motor 561 to lower the stacking tray 507 so that the distance from the height detection sensor 582 to the top surface of the sheets stacked on the stacking tray 507 becomes constant.

In step S1050, the CPU 120 obtains the position (height) of the stacking tray 507 based on signals transmitted from the tray detection sensors 571.

In step S1060, the CPU 120 determines whether the position of the stacking tray 507 is detected by the bottom end sensor 574. If it is determined that the position of the stacking tray 507 is detected by the bottom end sensor 574 (YES in step S1060), the CPU 120 advances the processing to step S1120 since the stacking tray 574 is full (hereinafter, referred to as tray full).

The processing performed in step S1120 will be described with reference to FIG. 5.

In step S2010, the CPU 120 issues an instruction to the marking unit 320 to stop printing. Here, the CPU 120 performs control to stop feeding sheets. The CPU 120 further performs control to discharge a sheet or sheets remaining in the sheet conveyance paths of the MFP 100 to the stacking tray 507. Of the sheets remaining in the sheet conveyance paths, one(s) on which an image has already been printed is/are simply discharged. One(s) on which no image has been printed yet is/are discharged after image printing.

In step S2020, the CPU 120 displays a tray full screen on the operation unit 170. FIG. 8 illustrates an example of the tray full screen displayed. In FIG. 8, the tray full screen displays a tray full error which has occurred on the stacking tray 507. The tray full screen also displays a message for prompting the user to remove the sheets stacked on the stacking tray 507. The tray full screen further displays a message for notifying that printing can be continued by removing the sheets, and a message for prompting the user to press a cancel key if the printing is to be cancelled. A cancel key 801 is a key for canceling the printing-stopped job.

In step S2030, the CPU 120 determines whether the sheets are removed from the stacking tray 507. If the sheet detection sensor 581 detects any sheet stacked on the stacking tray 507, the CPU 120 determines that the sheets are not removed from the stacking tray 507 (NO in step S2030), and advances the processing to step S2080. If the sheet detection sensor 581 does not detect any sheet stacked on the stacking tray 507, the CPU 120 determines that the sheets are removed from the stacking tray 507 (YES in step S2030), and advances the processing to step S2040.

In step S2080, the CPU 120 determines whether an instruction to cancel printing is accepted from the user via the cancel key 801. If the cancel key 801 is pressed, the CPU 120 determines that the instruction to cancel printing is accepted from the user (YES in step S2080), and advances the processing to step S2090. If it is determined that the cancel key 801 is not pressed (NO in step S2080), the CPU 120 returns the processing to step S2030.

In step S2090, the CPU 120 cancels the printing-stopped job, deletes information about the job from the nonvolatile memory 140, and ends the processing. While an example where the cancel key 801 is displayed on the tray full screen has been described, the cancel key 801 does not need to be displayed. In such a case, the CPU 120 repeats the processing of step S2030 until it is determined that the sheets are removed from the stacking tray 507 in step S2030.

If the processing has proceeded from step S2030 to step S2040, then in step S2040, the CPU 120 issues an instruction to the motor drive control unit 562 to drive the elevating motor 561 to lift the stacking tray 507.

In step S2050, the CPU 120 determines whether the stacking tray 507 has reached an initial position. If it is determined that the stacking tray 507 has not reached the initial position (NO in step S2050), the CPU 120 advances the processing to step S2060. If it is determined that the stacking tray 507 has reached the initial position (YES in step S2050), the CPU 120 advances the processing to step S1100 of FIG. 4. The initial position refers to a position where no sheet is stacked on the stacking tray 507 and the stacking tray 507 is ready to stack a discharged sheet. If the stacking tray 507 is detected by the top end sensor 573 of FIG. 2, the CPU 120 determines that the position of the stacking tray 507 has reached the initial position.

In step S2060, the CPU 120 determines whether an abnormality is detected when the stacking tray 507 is lifted. If it is determined that an abnormality is detected (YES in step S2060), the CPU 120 advances the processing to step S2070. If it is determined that an abnormality is not detected (NO in step S2070), the CPU 120 advances the processing to step S2040. For example, the CPU 120 detects an abnormality of the stacking tray 507 if the belt 554 is disengaged from the upper pulley 551 or the lower pulley 552 when the stacking tray 507 is lifted. The CPU 120 also detects an abnormality of the stacking tray 507 if the power of the elevating motor 561 is not transmitted to the upper pulley 551. Specifically, the CPU 120 may detect that the position of the stacking tray 507 detected by the tray detection sensors 571 does not ascend and remains unchanged although the elevating motor 561 is driven to lift the stacking tray 507. In such a case, the CPU 120 determines that an abnormality is detected when the stacking tray 507 is lifted.

In step S2070, the CPU 120 displays a service error illustrated in FIG. 9 on the operation unit 170, and ends the processing. FIG. 9 illustrates a screen displaying a message that repair is needed and a message for prompting the user to call a serviceperson. The screen also displays contact information for calling the serviceperson. Instead of displaying the message for prompting the user to call a serviceperson and the contact information about the serviceperson, the screen may display a message for prompting the user to call the administrator and contact information about the administrator.

As described above, in the present exemplary embodiment, the message for prompting the user to call a serviceperson is not displayed if the descending stacking tray 507 collides with an obstacle and cannot be lowered. On the other hand, if the ascending stacking tray 507 runs into an obstruction and cannot be lifted, the message for prompting the user to call a serviceperson is displayed.

Return to the description of step S1060 in the flowchart of FIG. 4.

In step S1060, if it is determined that the position of the stacking tray 507 is not detected by the bottom end sensor 574 (NO in step S1060), the CPU 120 advances the processing to step S1070.

In step S1070, the CPU 120 determines whether an abnormality is detected when the stacking tray 507 is lowered. If it is determined that an abnormality is detected (YES in step S1070), the CPU 120 advances the processing to step S1110. If it is determined that an abnormality is not detected (NO in step S1070), the CPU 120 advances the processing to step S1080. For example, the CPU 120 detects an abnormality if the lowering of the stacking tray 507 is obstructed by an obstacle placed under the stacking tray 507. Specifically, the CPU 120 detects that the position of the stacking tray 507 detected by the tray detection sensors 571 remains unchanged although the elevating motor 561 is driven to lower the stacking tray 507. In such a case, the CPU 120 determines that an abnormality is detected when the stacking tray 507 is lowered.

In step S1110, the CPU 120 determines whether the position of the stacking tray 507 is the initial position. If the position of the stacking tray 507 is not the initial position (NO in step S1110), the CPU 120 advances the processing to step S1130. If the position of the stacking tray 507 is the initial position (YES in step S1110), the CPU 120 advances the processing to step S1140.

If the processing has proceeded from step S1110 to step S1130, as illustrated in FIG. 12, the stacking tray 507 can only stack a smaller amount of sheets than the original maximum possible amount due to the obstacle placed under the stacking tray 507. In such a case, the user can select either to remove the obstacle placed under the stacking tray 507 to continue printing or to remove the sheets stacked on the stacking tray 507 to continue printing without removing the obstacle. To enable such a selection, the CPU 120 performs the processing of step S1130. The processing of step S1130 will be described in detail with reference to FIG. 6.

In step S3010, the CPU 120 issues an instruction to the marking unit 320 to stop printing. Here, the CPU 120 performs control to stop feeding sheets. The CPU 120 further performs control to discharge a sheet or sheets remaining in the sheet conveyance paths of the MFP 100 to the stacking tray 507. Of the sheets remaining in the sheet conveyance paths, one(s) on which an image has already been printed is/are simply discharged. One(s) on which no image has been printed yet is/are discharged after image printing.

In step S3020, the CPU 120 obtains the position of the stacking tray 507 based on the signals from the tray detection sensors 571.

In step S3030, the CPU 120 stores the obtained position of the stacking tray 507 in the nonvolatile memory 140 as a lowering limit position. The position of the stacking tray 507 is stored by storing information for identifying the tray detection sensor 571 detecting the stacking tray 507 at the point of step S3030, from among information for identifying the respective tray detection sensors 571. In the case of the example illustrated in FIG. 12, information for identifying the tray detection sensor 590 is stored.

In step S7010, the CPU 120 determines whether to prompt the user to remove the obstacle. Specifically, the CPU 120 refers to the nonvolatile memory 140 to check the information set in advance on the screen illustrated in FIG. 14 described above. If the information indicating the setting for prompting the removal of an obstacle is stored in the nonvolatile memory 140, the CPU 120 determines that the user should be prompted to remove the obstacle (YES in step S7010), and advances the processing to step S7011. On the other hand, if the information indicating the setting for not prompting the removal of an obstacle is stored in the nonvolatile memory 140, the CPU 120 determines that the user should not be prompted to remove the obstacle (NO in step S7010), and advances the processing to step S7012.

In step S7011, the CPU 120 displays a screen illustrated in FIG. 10 on the operation unit 170. The screen illustrated in FIG. 10 includes a message for prompting the user to remove the sheets stacked on the stacking tray 507 and a message for prompting the user to remove the obstacle placed under the stacking tray 507. The screen also displays a message for notifying that printing can be continued by removing the sheets stacked on the stacking tray 507 or removing the obstacle. The user views the screen and removes the sheets stacked on the stacking tray 507 or the obstacle that is not supposed to be placed under the stacking tray 507. A cancel key 805 is a key for canceling the printing-stopped job. An OK key 806 is a key for the user to press after removal of the obstacle. If the OK key 806 is detected to be pressed, the CPU 120 determines that the obstacle is removed.

In step S7012, the CPU 120 displays the screen illustrated in FIG. 8 on the operation unit 170. The screen illustrated in FIG. 8 is intended to prompt the user to remove the stacked sheets from the stacking tray 507. This screen does not include a message for prompting the user to remove the obstacle. In such a case, the user viewing the screen is likely to remove the sheets on the stacking tray 507. The obstacle placed under the stacking tray 507 is less likely to be removed. The cancel key 801 is a key for canceling the printing-stopped job.

In step S3050, the CPU 120 determines whether the sheets are removed from the stacking tray 507. If the sheet detection sensor 581 detects any sheet stacked on the stacking tray 507, the CPU 120 determines that the sheets are not removed from the stacking tray 507 (NO in step S3050), and advances the processing to step S3100. On the other hand, if the sheet detection sensor 581 does not detect any sheet stacked on the stacking tray 507, the CPU 120 determines that the sheets are removed from the stacking tray 507 (YES in step S3050), and advances the processing to step S3060.

In step S3100, the CPU 120 determines whether the obstacle is removed, based on whether the OK key 806 is pressed. Specifically, the CPU 120 determines whether the OK key 806 illustrated in FIG. 10 is pressed by the user. If it is determined that the OK key 806 is pressed (YES in step S3100), the CPU 120 advances the processing to step S3110. If it is determined that the OK key 806 is not pressed (NO in step S3100), the CPU 120 advances the processing to step S3120.

In step S3110, the CPU 120 clears the lowering limit position stored in the nonvolatile memory 140. The CPU 120 advances the processing to step S1100 of FIG. 4.

In step S3120, the CPU 120 determines whether an instruction to cancel printing is accepted from the user via the cancel key 805. If the cancel key 805 is pressed, the CPU 120 determines that the instruction to cancel printing is accepted from the user (YES in step S3120), and advances the processing to step S3130. If the cancel key 805 is not pressed (NO in step S3120), the CPU 120 returns the processing to step S3050.

In step S3130, the CPU 120 cancels the printing-stopped job, deletes the information about the job from the nonvolatile memory 140, and ends the processing.

If the processing has proceeded from step S3050 to step S3060, then in step S3060, the CPU 120 instructs the motor drive control unit 562 to drive the elevating motor 561 to lift the stacking tray 507.

In step S3070, the CPU 120 determines whether the stacking tray 507 has reached the initial position. If it is determined that the stacking tray 507 has no reached the initial position (NO in step S3070), the CPU 120 advances the processing to step S3080. If it is determined that the stacking tray 507 has reached the initial position (YES in step S3070), the CPU 120 advances the processing to step S1100 of FIG. 4.

In step S3080, the CPU 120 determines whether an abnormality is detected during the lifting of the stacking tray 507. If it is determined that an abnormality is detected (YES in step S3080), the CPU 120 advances the processing to step S3090. If it is determined that an abnormality is not detected (NO in step S3080), the CPU 120 advances the processing to step S3060. The method for detecting an abnormality in step S3080 is the same as that described in step S2060.

In step S3090, the CPU 120 displays the service error illustrated in FIG. 9 on the operation unit 170, and ends the processing. The screen illustrated in FIG. 9 displays the message indicating that repair is needed and the message for prompting the user to call a serviceperson. The screen also displays the contact information for calling the serviceperson.

Next, the processing of step S1140 in FIG. 4 will be described with reference to FIG. 7.

The processing illustrated in FIG. 7 is performed if the position of the stacking tray 507 is the initial position and it is determined that an abnormality is detected in the processing of FIG. 4.

In step S4010, the CPU 120 issues an instruction to the marking unit 320 to stop printing.

In step S4020, the CPU 120 displays a screen for prompting the removal of an obstacle on the operation unit 170. FIG. 11 illustrates an example of the displayed screen. In FIG. 11, the screen presents display indicating that an obstacle detection error has occurred on the stacking tray 507. The screen also displays a message for notifying that printing can be continued by removing the obstacle. The user views the screen and removes the obstacle placed under the stacking tray 507. A cancel key 808 is a key for canceling the printing-stopped job. An OK key 809 is a key for the user to press after removal of the obstacle. If the CPU 120 detects that the OK key 809 is pressed, the CPU 120 determines that the obstacle is removed.

In step S4030, the CPU 120 determines whether the obstacle is removed, based on whether the OK key 808 is pressed. Specifically, the CPU 120 determines whether the OK key 808 illustrated in FIG. 10 is pressed by the user. If it is determined that the OK key 808 is pressed (YES in step S4030), the CPU 120 advances the processing to step S1100 of FIG. 4. If it is determined that the OK key 808 is not pressed (NO in step S4030), the CPU 120 advances the processing to step S4040.

In step S4040, the CPU 120 cancels the printing-stopped job, deletes the information about the job from the nonvolatile memory 140, and ends the processing.

Next, the case when the processing has proceeded from step S1070 to step S1080 of FIG. 4 will be described described.

If the processing has proceeded from step S1070 to step S1080 of FIG. 4, then in step S1080, the CPU 120 obtains the lowering limit position stored in the nonvolatile memory 140. The lowering limit position is stored in the nonvolatile memory 140 by the CPU 120 in step S3030. Specifically, among the information for identifying the respective tray detection sensors 571, the information for identifying the tray detection sensor 571 detecting the stacking tray 507 at the point of step S3030 is stored in the nonvolatile memory 140.

In step S1090, the CPU 120 determines whether the position of the stacking tray 507 coincides with the lowering limit position which is the position of the tray detection sensor 571 identified by the obtained information. If it is determined that the position of the stacking tray 507 coincides with the lowering limit position (YES in step S1090), the CPU 120 advances the processing to step S1130. On the other hand, if it is determined that the position of the stacking tray 507 does not coincide with the lowering limit position (NO in step S1090), the CPU 120 advances the processing to step S1100.

In step S1130, the CPU 120 performs the processing described with reference to FIG. 6.

If the processing has proceeded from step S1090 to step S1100, then in step S1100, the CPU 120 determines whether the printing is completed. If it is determined that the printing is not completed (NO in step S1100), the CPU 120 returns the processing to step S1020. If it is determined that the printing is completed (YES in step S1100), the CPU 120 ends the processing.

According to the present exemplary embodiment, after the lowering of the stacking tray 507 is obstructed by an obstacle, the user can remove the sheets stacked on the stacking tray 507 to resume printing. After the printing is resumed, the sheet discharge operation can be resumed while reducing the possibility that the stacking tray 507 collides with the obstacle again under imposed load and the stacking tray 507 and/or the elevating motor 561 is broken.

The administrator can set whether to prompt the user to remove an obstacle placed under the stacking tray 507 if the lowering of the stacking tray 507 is obstructed by the obstacle.

The administrator may want the user to use the MFP 100 by removing an obstacle if the obstacle is detected during a sheet stacking operation. In such a case, the administrator can make a setting to prompt the removal of the obstacle. On the other hand, if the administrator wants the user to use the MFP 100 with an obstacle intentionally placed under the stacking tray 507, the administrator can make a setting for not prompting the removal of the obstacle.

The foregoing exemplary embodiment has dealt with the case where the lowering limit position is stored and the lowering of the stacking tray 507 is stopped at the lowering limit position.

A second exemplary embodiment describes a case where the lowering of the stacking tray 507 is stopped at a position which is a predetermined height higher than the lowering limit position.

An MFP 100 according to the present exemplary embodiment has a configuration similar to that of the first exemplary embodiment described with reference to FIGS. 1 to 3. A detailed description thereof will thus be omitted. Only differences from the first exemplary embodiment will be described.

The CPU 120 according to the present exemplary embodiment performs control illustrated in the flowchart of FIG. 13 instead of FIG. 4. The processing illustrated in the flowchart of FIG. 13 is performed by the CPU 120 reading a program stored in the ROM 160 into the RAM 150 and executing the program.

Differences from FIG. 4 is steps S5010 and S5020.

In step S1080, the CPU 120 obtains the lowering limit position stored in the nonvolatile memory 140. The CPU 120 then advances the processing to step S5010.

In step S5010, the CPU 120 sets a position which is a predetermined height higher than the lowering limit position obtained in step S1080 as a new lowering limit position, and stores the new lowering limit position in the nonvolatile memory 140. The CPU 120 performs the processing of step S5010, for example, by storing information for identifying the tray detection sensor 571 arranged in a position one step higher than the tray detection sensor 571 identified in step S3030.

The predetermined height may be a fixed value determined in advance at the time of factory shipment. The predetermined height may be changed by the user via the operation unit 170 or an external apparatus. For example, suppose that a predetermined height of 10 cm is accepted from the user, and the plurality of tray detection sensors 571 illustrated in FIG. 2 is arranged at intervals of 5 cm. In such a case, the CPU 120 divides 10 cm by 5 cm to determine the tray detection sensor 571 positioned two steps higher than the tray detection sensor 571 identified by the information obtained in step S1080. The CPU 120 then sets the information for identifying the determined tray detection sensor 571 as a new lowering limit position.

In step S5020, the CPU 120 determines whether the position of the stacking tray 507 coincides with the lowering limit position which is the position of the tray detection sensor 571 identified by the information set in step S5010. If it is determined that the position of the stacking tray 507 coincides with the lowering limit position (YES in step S5020), the CPU 120 advances the processing to step S1130. If it is determined that the position of the stacking tray 507 is does not coincide with the lowering limit position (NO in step S5020), the CPU 120 advances the processing to step S1100.

In step S1130, the CPU 120 performs the processing described with reference to FIG. 6.

If the processing has proceeded from step S5020 to step S1100, then in step S1100, the CPU 120 determines whether the printing is completed. If it is determined that the printing is not completed (NO in step S1100), the CPU 120 returns the processing to step S1020. If it is determined that the printing is completed (YES in step S1100), the CPU 120 ends the processing.

By the foregoing control, after the lowering of the stacking tray 507 is obstructed by an obstacle, the user can resume printing by removing the sheets stacked on the stacking tray 507.

Since the predetermined height is changeable by the user, the user can increase the predetermined height to reduce the possibility that the stacking tray 507 comes into contact with the obstacle. The user can set the predetermined height to be smaller to increase the stacking capacity of sheets.

The administrator may want the user to use the MFP 100 by removing an obstacle if the obstacle is detected during a sheet stacking operation. In such a case, the administrator can make a setting to prompt the removal of the obstacle. On the other hand, if the administrator wants the user to use the MFP 100 with an obstacle intentionally placed under the stacking tray 507, the administrator can make a setting for not prompting the removal of the obstacle.

The foregoing exemplary embodiments have dealt with the case where the user sets whether to display the message for prompting the removal of an obstacle if the obstacle is detected during a sheet discharge operation.

In a third exemplary embodiment, the message for prompting the removal of an obstacle is not displayed if the position of the stacking tray 507 when the obstacle is detected is the same as that of the stacking tray 507 when an obstacle was detected last time. On the other hand, if the position of the stacking tray 507 when an obstacle is detected is different from that of the stacking tray 507 when an obstacle was detected last time, a new obstacle not intended by the administrator may have been placed. In such a case, the message for prompting the removal of an obstacle is displayed. An example will be described below.

An MFP 100 according to the present exemplary embodiment has a configuration similar to that of the first exemplary embodiment described with reference to FIGS. 1 to 3. A detailed description thereof will be omitted. Only differences from the first exemplary embodiment will be described.

The administrator initially operates a screen illustrated in FIG. 15 instead of the screen illustrated in FIG. 14 for situations where an obstacle is detected. Using the screen illustrated in FIG. 15, the administrator sets in advance whether to display a screen for prompting the removal of an obstacle if the obstacle is detected.

The screen illustrated in FIG. 15 includes a key 1405 for prompting the removal of an obstacle according to the position of the stacking tray 507, in addition to the key 1401 for prompting the removal of an obstacle and the key 1402 for not prompting the removal of an obstacle. Suppose that the administrator selects the “prompt removal of obstacle according to position of stacking tray” key 1405 and presses the OK key 1403. In such a case, the CPU 120 performs control so that information indicating the setting to prompt the removal of an obstacle according to the position of the stacking tray 507 if the obstacle is detected is stored in the nonvolatile memory 140.

If the administrator presses the cancel key 1404, the CPU 120 ends displaying the screen of FIG. 15 without storing information about any key selected on the screen illustrated in FIG. 15 into the nonvolatile memory 140.

The CPU 120 according to the present exemplary embodiment performs control illustrated in the flowchart of FIG. 16 instead of FIG. 6. The processing illustrated in the flowchart of FIG. 16 is performed by the CPU 120 reading a program stored in the RAM 160 into the RAM 150 and executing the program. Differences from FIG. 6 are steps S8000, S8010, and S8011.

In step S8000, the CPU 120 stores the position of the stacking tray 507 obtained in step S3020 into the nonvolatile memory 140 as a new lowering limit position instead of the lowering limit position stored last time. Storing the position of the stacking tray 507 obtained in step S3020 instead of the lowering limit position stored last time means storing the position without overwriting the lowering limit position stored last time. For example, the position of the stacking tray 507 obtained in step S3020 is stored in a different storage area on the nonvolatile memory 140.

In step S7010, the CPU 120 determines whether to prompt the removal of the obstacle. Specifically, the CPU 120 refers to the nonvolatile memory 140 and checks the setting made on the screen illustrated in FIG. 15 as described above. If the information indicating the setting for prompting the removal of an obstacle is stored in the nonvolatile memory 140, the CPU 120 determines to prompt the removal of the obstacle (YES in step S7010), and advances the processing to step S7011. On the other hand, if the information indicating the setting for not prompting the removal of an obstacle is stored in the nonvolatile memory 140 (NO in step S7010 and YES in step S8010), the CPU 120 advances the processing to step S7012. If the information indicating the setting for prompting the removal of an obstacle according to the position of the stacking tray 507 is stored in the nonvolatile memory 140 (NO in step S7010 and NO in step S8010), the CPU 120 advances the processing to step S8011.

In step S8011, the CPU 120 performs screen display processing according to the position of the stacking tray 507.

Detailed processing of step S8011 will be described with reference to FIG. 17.

The processing illustrated in the flowchart of FIG. 17 is performed by the CPU 120 reading a program stored in the RAM 160 into the RAM 150 and executing the program.

In step S9010, the CPU 120 determines whether the new position of the stacking tray 507 obtained in step S3020 of FIG. 16 is the same as the position of the stacking tray 507 stored when the stacking tray 507 collided with an obstacle and could not be lowered last time. Specifically, the CPU 120 determines whether the position of the stacking tray 507 having been stored as the lowering limit position in the nonvolatile memory 140 and the new position of the stacking tray 507 obtained in step S3020 are the same. The position of the stacking tray 507 is stored by storing the information for identifying the tray detection sensor 571 that is detecting the stacking tray 507 at the point of step S3030 among the information for indicating the respective tray detection sensors 571. In the case illustrated in FIG. 12, the information for identifying the tray detection sensor 590 is stored as the position of the stacking tray 507. If the new position of the stacking tray 507 obtained in step S3020 of FIG. 16 is determined to be the same as the position of the stacking tray 507 when the stacking tray 507 collided with an obstacle and could not be lowered last time (YES in step S9010), the CPU 120 advances the processing to step S9020. On the other hand, if the new position of the stacking tray 507 obtained in step S3020 of FIG. 16 is determined not to be the same as the position of the stacking tray 507 when the stacking tray 507 collided with an obstacle and could not be lowered last time (NO in step S9010), the CPU 120 advances the processing to step S9030.

In step S9020, the CPU 120 displays the screen illustrated in FIG. 8 on the operation unit 170. The screen illustrated in FIG. 8 is a screen for prompting the removal of the stacked sheets from the stacking tray 507. This screen does not include a message for prompting the removal of an obstacle. In such a case, the user viewing the screen is likely to remove the sheets on the stacking tray 507. The obstacle placed under the stacking tray 507 is less likely to be removed. The cancel key 801 is a key for canceling the printing-stopped job. The cancel key 801 does not need to be displayed.

In step S9030, the CPU 120 displays the screen illustrated in FIG. 10 on the operation unit 170. The screen illustrated in FIG. 10 includes the message for prompting the user to remove the sheets stacked on the stacking tray 507 and the message for prompting the user to remove the obstacle placed under the stacking tray 507. The screen also displays the message for notifying that printing can be continued by removing the sheets stacked on the stacking tray 507 or removing the obstacle. The user views the screen and removes the sheets stacked on the stacking tray 507 or the obstacle that is not supposed to be placed under the stacking tray 507. The cancel key 805 is a key for canceling the printing-stopped job. The OK key 806 is a key for the user to press after removal of the obstacle. If the pressing of the OK key 806 is detected, the CPU 120 determines that the obstacle is removed.

By the foregoing control, the removal of an obstacle can be prompted if another new obstacle is placed on an obstacle intentionally placed by the administrator or if a different obstacle is placed instead of the obstacle intentionally placed by the administrator.

On the other hand, if an obstacle is placed which is the same as the obstacle which the stacking tray 507 collided with and could not be lowered last time, the message for prompting the removal of the obstacle is not displayed. This can prevent removal of the obstacle despite the intention of the administrator.

In the foregoing third exemplary embodiment, prompting the removal of an obstacle is determined according to whether the position of the tray 507 when the tray 507 collides with the obstacle is the same as the tray 507 when it collided with an obstacle last time.

A fourth exemplary embodiment deals with a control example where a counter is incremented if the position of the stacking tray 507 when the tray 507 collides with an obstacle is the same as the tray 507 when the it collided with an obstacle last time. The CPU 120 prompts the removal of the obstacle before the value of the counter reaches a predetermined value of N. After the value of the counter has reached N, the CPU 120 does not prompt the removal of the obstacle.

Consequently, before the stacking tray 507 is obstructed by the obstacle N times, a message for prompting the removal of the obstacle can be displayed to prompt the user to remove the obstacle. Further, if the stacking tray 507 is obstructed by the obstacle N times, the display of the message for prompting the removal of the obstacle can be automatically ended since the obstacle has possibly been intentionally placed.

A configuration and control of the MFP 100 according to the present exemplary embodiment are similar to those of the third exemplary embodiment. A detailed description thereof will thus be omitted. Only differences from the third exemplary embodiment will be described.

In the present exemplary embodiment, control illustrated in the flowchart of FIG. 18 is performed instead of FIG. 17 described in the third exemplary embodiment.

In the present exemplary embodiment, the CPU 120 stores a variable T and a threshold N in the nonvolatile memory 140. The variable T is intended to count the number of times the positions where an obstacle is detected coincide with each other. The CPU 120 performs control according to the values of the variable T and the threshold N stored.

The CPU 120 according to the present exemplary embodiment performs the control illustrated in the flowchart of FIG. 18 instead of FIG. 17. The processing illustrated in the flowchart of FIG. 18 is performed by the CPU 120 reading a program stored in the ROM 160 into the RAM 150 and executing the program. Differences from the third exemplary embodiment are steps S10010, S10020, and S10030.

In step S9010, the CPU 120 determines whether the new position of the stacking tray 507 obtained in step S3020 of FIG. 16 is the same as the position of the stacking tray 507 when the stacking tray 507 collided with an obstacle and could not be lowered last time. The determination method is similar to that described in the third exemplary embodiment.

If the new position of the stacking tray 507 obtained in step S3020 of FIG. 16 is determined to be the same as the position of the stacking tray 507 when the stacking tray 507 collided with an obstacle and could not be lowered last time (YES in step S9010), the CPU 120 advances the processing to step S10010. On the other hand, if the new position of the stacking tray 507 obtained in step S3020 of FIG. 16 is determined not to be the same as the position of the stacking tray 507 when the stacking tray 507 collided with an obstacle and could not be lowered last time (NO in step S9010), the CPU 120 advances the processing to step S10030.

In step S10010, the CPU 120 increases the number of times T stored in the nonvolatile memory 140, that the obstacle detected positions coincide with each other, by one. The CPU 120 then advances the processing to step S10020.

In step S10020, the CPU 120 determines whether the number of times T that the positions where an obstacle is detected coincide with each other is less than N. If the number of times T that the positions where an obstacle is detected coincide with other is less than N (YES in step S10020), the CPU 120 advances the processing to step S9030. On the other hand, if the number of times T that the positions where an obstacle is detected coincide with each other is greater than or equal to N (NO in step S10020), the CPU 120 advances the processing to step S9020.

In step S9020, the CPU 120 displays the screen illustrated in FIG. 8 on the operation unit 170. The screen illustrated in FIG. 8 is a screen for prompting the removal of the stacked sheets from the stacking tray 507. This screen does not include a message for prompting the removal of an obstacle. The cancel key 801 is a key for canceling the printing-stopped job. The cancel key 801 does not need to be displayed.

In step S9030, the CPU 120 displays the screen illustrated in FIG. 10 on the operation unit 170. The screen illustrated in FIG. 10 includes the message for prompting the user to remove the sheets stacked on the stacking tray 507 and the message for prompting the user to remove the obstacle placed under the stacking tray 507. The screen also displays the message for notifying that printing can be continued by removing the sheets stacked on the stacking tray 507 or removing the obstacle. The cancel key 805 is a key for canceling the printing-stopped job. The OK key 806 is a key for the user to press after removal of the obstacle. If the pressed OK key 806 is detected, the CPU 120 determines that the obstacle is removed.

By the foregoing control, the CPU 120 displays the message for prompting the removal of the obstacle before the lowering of the stacking tray 507 is obstructed by the obstacle N times. After the lowering is obstructed by the obstacle N times, the CPU 120 ends displaying the message for prompting the removal of the obstacle.

Before the stacking tray 507 is obstructed by the obstacle N times, the message for removing the obstacle can be displayed to prompt the user to remove the obstacle. If the stacking tray 507 is obstructed by the obstacle N times, the display of the message for prompting the removal of the obstacle can be automatically ended since the obstacle has possibly been intentionally placed.

The value of N described in the present exemplary embodiment may be a fixed value set in the factory at the time of shipment of the MFP 100. The value of N may be changed by the administrator or the user via the operation unit 170.

Other Exemplary Embodiments

The foregoing exemplary embodiments have dealt with the case where the height of the stacking tray 507 is detected by the tray detection sensor 571. The method for detecting the height of the stacking tray 507 is not limited thereto. For example, by using a sensor for counting the protruded portions of concavity and convexity of the belt 554 for elevating the stacking tray 507, the CPU 120 may recognize the position of the stacking tray 507 according to the number of protruded portions counted from the initial position of the stacking tray 507. For example, if the protruded portions of the concavity and convexity are arranged at a pitch of 5 mm and the number of protruded portions counted from the initial position of the stacking tray 507 is 50, the CPU 120 recognizes that the stacking tray 507 is positioned 250 mm below the initial position. If such a method is applied, the position of the stacking tray 507 at the point when an obstacle is detected can be stored as X mm. After printing and stacking are resumed, the lowering of the stacking tray 507 may be stopped at X mm. Alternatively, the lowering of the stacking tray 507 may be stopped at Y mm which is obtained by subtracting a predetermined height from X. As described in the second exemplary embodiment, the predetermined height may be a fixed value determined in advance at the time of factory shipment, like 5 cm and 10 cm. The predetermined height may also be changed by the user via the operation unit 170 or an external apparatus.

Further, the CPU 120 may identify the amount of rotation of the elevating motor 561 for elevating the stacking tray 507, and recognize the position of the stacking tray 507 based on the amount of rotation identified on the basis of the initial position of the stacking tray 507. For example, if the elevating motor 561 is a stepping motor, the CPU 120 can find out how much the stacking tray 507 is moved from the initial position of the stacking tray 507, based on the product of the movement amount of the stacking tray 507 per step and the number of steps (the number of pulses) of rotation. The CPU 120 can thus recognize the position of the stacking tray 507 based on the found amount of movement from the initial position. If the elevating motor 561 is a direct-current (DC) motor, the CPU 120 can recognize the position of the stacking tray 507 based on the amount of movement of the stacking tray 507 which is determined based on the amount of rotation of the DC motor.

The foregoing exemplary embodiments have dealt with the case where the occurrence of an abnormality due to an obstacle when the stacking tray 507 is lowered is detected by the following method. That is, the CPU 120 detects that the position of the stacking tray 507 detected by the tray detection sensor 571 does not vary although the elevating motor 561 is rotated in the direction of lowering the stacking tray 507 by the belt 554. In such a case, the CPU 120 determines that an abnormality has occurred due to an obstacle when the stacking tray 507 is lowered. However, an exemplary embodiment of the present invention is not limited thereto. A sensor for detecting an obstacle may be provided under the stacking tray 507 to detect that the lowering of the stacking tray 507 is obstructed by an obstacle.

OTHER EMBODIMENTS

Embodiments of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions recorded on a storage medium (e.g., non-transitory computer-readable storage medium) to perform the functions of one or more of the above-described embodiment(s) of the present invention, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more of a central processing unit (CPU), micro processing unit (MPU), or other circuitry, and may include a network of separate computers or separate computer processors. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2013-248035 filed Nov. 29, 2013, which is hereby incorporated by reference herein in its entirety. 

What is claimed is:
 1. A sheet stacking apparatus comprising: a lowering control unit configured to lower a sheet stacking unit according to an amount of sheets stacked; a determination unit configured to determine that the sheet stacking unit cannot be lowered by the lowering control unit; a setting unit configured to set whether to prompt a user to remove an object placed under the sheet stacking unit if the determination unit determines that the sheet stacking unit cannot be lowered while sheets are being stacked on the sheet stacking unit; and a notification unit configured to, if it is set by the setting unit to prompt the user to remove the object placed under the sheet stacking unit, make a notification for prompting the user to remove the object placed under the sheet stacking unit, and if it is not set by the setting unit to prompt the user to remove the object placed under the sheet stacking unit, not make the notification.
 2. The sheet stacking apparatus according to claim 1, wherein the notification unit is configured to, if it is not set by the setting unit to prompt the user to remove the object placed under the sheet stacking unit, not make the notification and notify the user to remove a sheet or sheets stacked on the sheet stacking unit.
 3. The sheet stacking apparatus according to claim 1, further comprising a control unit configured to, if the determination unit determines that the sheet stacking unit cannot be lowered while sheets are being stacked on the sheet stacking unit, store a position of the sheet stacking unit in a storage unit and stop stacking sheets on the sheet stacking unit, and if a sheet or sheets stacked on the sheet stacking unit is/are removed while the stacking of sheets on the sheet stacking unit is being stopped, lift the sheet stacking unit and stack sheets on the lifted sheet stacking unit, wherein the notification unit is configured to, when the determination unit determines that the sheet stacking unit cannot be lowered, while sheets are being stacked on the lifted sheet stacking unit, and if the position of the sheet stacking unit is different from the position of the sheet stacking unit stored in the storage unit, make the notification, and when the determination unit determines that the sheet stacking unit cannot be lowered while sheets are being stacked on the lifted sheet stacking unit, and if the position of the sheet stacking unit coincides with the position of the sheet stacking unit stored in the storage unit, not make the notification.
 4. The sheet stacking apparatus according to claim 1, comprising a control unit configured to, if the determination unit determines that the sheet stacking unit cannot be lowered while sheets are being stacked on the sheet stacking unit, store a position of the sheet stacking unit in a storage unit and stop stacking sheets on the sheet stacking unit, and if a sheet or sheets stacked on the sheet stacking unit is/are removed while the stacking of sheets on the sheet stacking unit is being stopped, lift the sheet stacking unit and stack sheets on the lifted sheet stacking unit, wherein the notification unit further includes an identification unit configured to identify a number of times that the position of the sheet stacking unit, when the determination unit determines that the sheet stacking unit cannot be lowered, and while sheets are being stacked on the lifted sheet stacking unit, coincides with the position of the sheet stacking unit stored in the storage unit, and wherein the notification unit is configured to, if the number of times identified by the identification unit is less than N, make the notification, and if the number of times identified by the identification unit is greater than or equal to N, not make the notification.
 5. The sheet stacking apparatus according to claim 4, further comprising an acceptance unit configured to accept a value of the N from the user.
 6. The sheet stacking apparatus according to claim 1, wherein the control unit is configured to, if the object placed under the sheet stacking unit is removed while the stacking of sheets on the sheet stacking unit is being stopped, perform control to resume stacking of the sheets on the sheet stacking unit, and the lowering control unit is configured to lower the sheet stacking unit without lifting the sheet stacking unit from a position at which the stacking of sheets is stopped.
 7. The sheet stacking apparatus according to claim 1, wherein the control unit is configured to, if an instruction to cancel a job for stacking sheets is accepted while stacking of the sheets on the sheet stacking unit is being stopped, cancel the job for stacking the sheets.
 8. The sheet stacking apparatus according to claim 1, wherein the control unit is configured to, if the sheet stacking unit cannot be lifted when the sheet stacking unit is lifted after a sheet stacked on the sheet stacking unit has been removed, perform control to display a screen for calling a serviceperson on a display unit.
 9. The sheet stacking apparatus according to claim 1, further comprising a printing unit configured to print an image on a sheet, wherein the sheet stacking unit is configured to stack sheets on which an image is printed by the printing unit.
 10. The sheet stacking apparatus according to claim 9, further comprising a reading unit configured to read an image of a document, wherein the printing unit is configured to print the image read by the reading unit.
 11. A method for controlling a sheet stacking apparatus having a lowering control unit configured to lower a sheet stacking unit according to an amount of sheets stacked, the method comprising: determining that the sheet stacking unit cannot be lowered by the lowering control unit; setting whether to prompt a user to remove an object placed under the sheet stacking unit if it is determined that the sheet stacking unit cannot be lowered while sheets are being stacked on the sheet stacking unit; and if it is set by the setting to prompt the user to remove the object placed under the sheet stacking unit, making a notification for prompting the user to remove the object placed under the sheet stacking unit, and if it is not set by the setting to prompt the user to remove the object placed under the sheet stacking unit, not making the notification.
 12. A computer-readable storage medium storing a program for causing a computer to perform a method for controlling a sheet stacking apparatus having a lowering control unit configured to lower a sheet stacking unit according to an amount of sheets stacked, the method comprising: determining that the sheet stacking unit cannot be lowered by the lowering control unit; setting whether to prompt a user to remove an object placed under the sheet stacking unit if it is determined that the sheet stacking unit cannot be lowered while sheets are being stacked on the sheet stacking unit; and if it is set by the setting to prompt the user to remove the object placed under the sheet stacking unit, making a notification for prompting the user to remove the object placed under the sheet stacking unit, and if it is not set by the setting to prompt the user to remove the object placed under the sheet stacking unit, not making the notification. 